Preparation of Media 127 
The lists of glassware necessary for plating one 
sample of milk and for preparing one liter of medium, 
together with the necessary materials and apparatus, 
are given at the end of this chapter, the actual amcunts 
being left to the discretion of the individual. They 
may be readily secured from any firm dealing in such 
materials. . 
Some sort of an incubator is necessary. Very satis- 
factory incubators are specially built for bacteriolog- 
ical purposes, but, if it is necessary to economize, it 
is possible to convert a poultry incubator for the pur- 
pose, or a home-made incubator may be cheaply and 
simply built by anyone with a little ingenuity. An 
asbestos-lined box fitted with an electric light and 
thermostat is very satisfactory. The one factor neces- 
sary is a constant temperature of 37° C. or 98.6° F. 
Media.—It is possible to obtain agar or gelatine 
already prepared from various bacteriological labora- 
tories. If, however, it is found necessary to make 
the medium, the following directions may be used: 
As a basis for this médium use nutrient bouillon, or 
broth. This may be made either from the ground 
beef or beef extract. Directions for making the bouil- 
lon from ground beef are found in Moore’s Laboratory 
Directions for Beginners in Bacteriology. It is much 
easier to use beef extract and, for general purposes, 
entirely satisfactory. 
Measure out the following: 
Water ee Sie Sarge rea a merece tig: cele ie Mar leerancg . 1 liter 
Liebig’s Extract of Beef. . «2... ee sees -.  . 8 grams 
Peptone (Wittes) . .....-. Bae Eee ew oe 10 grams 
